Find the sum of all natural number less than 100 which are divisible b

1.	Find the sum of all natural number less than 100 which are divisible by 5
Answer» Last term should be 95 not 100 bcos in question it is less than 100 so sum will be 950 Parishi ur answer is wrong AP formed will be-5,10,15.......100So, a=5d=5an=100n=? an= a+(n-1)d 100=5+(n-1)5 95= 5n-5 5n = 100 n=20 Putting these values in the sum formula we get, Sn=n/2 [ 2a+(n-1)d] S20= 20/2 [ 2(5) + (19)5] S20=10[10+95] S20=10[105] S20=1050 ANS.Hope it helps

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